For example, in a kind of a music library, if we have artists, albums and tracks, and each of them has a few attributes, and some attributes are numeric, some are sets of tags (where order is not important), some are lists (where order is important).
We'd need to edit, browse, filter this data dynamically, do basic calculations, and keep relations between entities.

Spreadsheet programs and the functions they offer are bound to the paradigm of information ordered in a 2-dimensional grid. XML is completely different – information is represented as a tree. Can you give an example of what data you have and what you want to do with it?
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slhck♦Mar 2 '12 at 15:05

For example, in a kind of a music library, if we have artists, albums and tracks, and each of them has a few attributes, and some attributes are numeric, some are sets of tags (where order is not important), some are lists (where order is important). And we need to edit, browse, filter this data dynamically, do basic calculations, and to keep relations between entities.
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OgnjenMar 2 '12 at 15:38

As the comment by @slchk states, there is a difference in the foundations of a spreadsheet's use and XML which is tree based. The spreadsheet is 2D and XML is better for a directory structure of music like you suggest, I have briefly been introduced to oxygenxml link which has many nice views. It has a nice interface for editing data manually, but I don't know how well it interfaces with maybe your own scripts etc. But I guess you could work with the xml it exports.